Research on analytical ultracentrifugation encompasses the following areas: The determination of molecular weight averages from routine sedimentation velocity experiments using the Rayleigh and absorption optical systems, the calculation of molecular configurations from hydrodynamic measurements, and the development of automatic data collection and processing methods. Studies of the high pH self-association of alpha-chymotrypsin are proposed to determine the stoichiometries and mechanisms of aggregation of this protein as a model. Colchicine binding proteins of porcine brain are under investigation. The mechanism of binding of colchicine to tubulin is being studied. The particulate protein has been solubilized and is being characterized relative to the soluble protein. Polypeptide chain cleavage and separation methods are being investigated to determine the primary structure of the protein. The hypothesis that the trypsin-related serine proteases, proinsulins and immuno-globins are sequence-homologous is being tested using computer techniques. The possibility that the three-dimensional structures of proteins can be aligned is to be tested also. Rheumatoid factors (IgG) of patients with rheumatoid arthritis are under investigation. Solid evidence from one patient and preliminary evidence from a second indicates that these complexes constitute a self-associating system.